Obituaries

Alastair G.W. Cameron, an astrophysicist who was among the first to develop the now widely accepted theory that the moon was formed after a planet collided with Earth billions of years ago, has died. He was 80.

Cameron, who also mapped out planetary exploration for the U.S. space program, died of heart failure Oct. 3 at his home in Tucson, his family said.

His "giant impact" theory held that the moon was created after an object the size of Mars struck Earth, sending a ring of debris into space that eventually coalesced into the moon.

At first the theory, published in 1976, was ridiculed. About a decade later, it became accepted in the scientific mainstream as separate computer simulations reached the same conclusion.

"He had a lot of brilliant ideas. He was often five steps ahead of everybody else," said Katharina Lodders, a research professor at Washington University in St. Louis who was his last collaborator. "He was the Cameron, one of the really big guys in the field."

Taken with unraveling the mysteries of the universe, Cameron helped devise a theory on how supernovas, or large dying stars, appear to create new stars as they explode. In the 1950s, he also figured out how chemical elements formed inside stars.

Alastair Graham Walter Cameron was born June 21, 1925, in Winnipeg, Canada. The son of a biochemist, he earned a bachelor's degree from the University of Manitoba in 1947 and a doctorate in nuclear physics from the University of Saskatchewan in 1952.

After teaching at Harvard University for 26 years, he became a senior research scientist in 1999 at the Lunar and Planetary Laboratory at the University of Arizona in Tucson.

At the laboratory, Cameron's computers continue to hum away doing calculations -- the staff is reluctant to turn off the machines, which could produce one last theory.

The former Elizabeth MacMillan, Cameron's wife of 46 years, died in 2001. He is survived by a sister.